We have no way of knowing how rare intelligent beings are in the universe, or even what constitutes intelligence (how else could a species be intelligent?) but the ability to travel interstellar space is most likely extremely rare, and even with a billion years head start, one civilization is unlikely to have made it very far (especially if their version of NASA gets its budget cut every time the politicians are looking for a tax break for the middle class).

If we ever get to the point where we can move beyond Earth (and we have to eventually if we are not to be snuffed out with our temporarily life-sustaining planet), we will have to go looking for another planet that can support life, and if it is already occupied, which it probably would be if it’s a good candidate, we might find ourselves the illegal aliens. Good real estate is hard to find.

My personal suspicion of why we don’t find alien radio signals is that it may be best to be quiet. Do we really want to advertise our nice beaches and tasty humans to the rest of the universe?

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J.K. Fausnight

When I was 15 years old, I could no longer reconcile religion with reality, and I knew one of them would have to go. It still amazes me how many people make the other choice.

Maybe the aliens are so much more evolved and advanced compared to us that we cannot be aware of their existence. Just like a mushroom has no idea when you are standing two inches away from it. I sometimes wonder if being able to think and love is as good as it gets in this universe…

In the past,Barto,there were no chloroflourocarbons,no PCB’s(which are now outlawed in most places,but there legacy continues),no CO2 emmisions,no above and below ground nuclear tests,etc.etc.

So are you advocating a return to simpler times (technologically speaking)? How do we start?

Hi Shawn.No, I’m not advocating a return to simpler times.Just a real “revolution?” of awareness on the part of world leaders to really address these problems.You know-what most rational environmentalists are crying out for.

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Row row row your boat gently down the stream. Merrily Merrily merrily merrily life is but a dream!

England and industrial Europe in the 1800s was incredibly polluted. There were very real health consequences caused by the very poor air quality. The water was polluted, and much of if was not what we would consider potable, the germ theory was not understood, and indoor plumbing was not in all homes. Horse and other animal droppings littered the roads, and people rarely bathed. Spice to disguise spoilage was as important as use as a flavoring agent. I could go on and on and on in this vein. We survived, we solved problems. We can do it again…...

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Church; where sheep congregate to worship a zombie on a stick that turns into a cracker on Sundays…

The question, asanta, is how many of us will survive? This planet cannot sustain six billion people indefinitely.

The problem here is that we cannot smoothly scale down. The economic system we have built presumes the economic interaction of all those billions of people. If we randomly remove, say, 10% of those people, then the system simply collapses. That’s because each component of the system requires the inputs from a great many other components; if even one of those inputs disappears, then the component cannot function and its failure propagates through the system. If the system starts to collapse, there is no natural stopping point before we get all the way down to hunter-gatherer lifestyles.

If the system starts to collapse, there is no natural stopping point before we get all the way down to hunter-gatherer lifestyles.

Well, this hasn’t really been demonstrated. It is a semi-plausible hypothesis, but it’s equally (perhaps more) plausible that people, being generally industrious and inventive, will be able to figure out how to fill in. Of course, all depends on the percentages. I don’t expect that a 10% loss would be literally catastrophic, but a pandemic on the order of the Black Death, with losses potentially greater than 50% would be a different thing entirely. I fear it is only a matter of time.

There is a natural stopping point, Chris. We do not have to return to hunter-gatherer societies. We have the accumulated knowledge of 400 years of science. We can use that knowledge to comfortably sustain a population well below the present population, probably closer to to the 1850s population (1.5 billion) than the 6 billion+ we now (mostly) sustain. But…

Human nature being what it is, I doubt we’ll see a peaceful transition in most of the world. Losing 75 percent of our population will be nasty, brutish, and bloody as people use any means available to feed their families. The more developed countries will not suffer as badly, but even in the United States things could get very ugly when the stores cannot provide enough food to feed everyone in their neighborhoods.

Developing new energy sources will take decades, during which people will be starving, oil will become scarcer and more expensive, and resource wars a chilling possibility.

I hope these things do not happen in my lifetime, while I fear what await future generations. It could take several centuries to return to what our descendants may consider a normal life. Or it may take decades. Either way, it won’t be pretty.

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You cannot have a rational conversation with someone who holds irrational beliefs.

There’s a very important relationship at work here: any given level of technology requires a certain size population. If we were to take an entire library of science and technology books and send them in a time machine back to the Roman Empire, we would most definitely NOT see Roman soldiers wiping out barbarians with machine guns and Stealth bombers. They simply did not have the population to sustain the industrial base necessary for all that technology. Thus, reductions in population will necessarily entail reductions in the technological base—which in turn will lead to greater reductions in technology. Just as it was a virtuous circle on the way up, it’s a vicious circle on the way down.

There’s a very important relationship at work here: any given level of technology requires a certain size population. If we were to take an entire library of science and technology books and send them in a time machine back to the Roman Empire, we would most definitely NOT see Roman soldiers wiping out barbarians with machine guns and Stealth bombers. They simply did not have the population to sustain the industrial base necessary for all that technology.

Agreed. However with those books and a few hundred years they might well be beginning their industrial revolution. It’s not hard to build waterwheels and steam engines if you know what you’re doing.

Chris Crawford - 31 October 2008 08:02 PM

Thus, reductions in population will necessarily entail reductions in the technological base—which in turn will lead to greater reductions in technology. Just as it was a virtuous circle on the way up, it’s a vicious circle on the way down.

Well, again, this is an empirical claim which is questionable, at least as regards the percentages. As I say, I disagree that a 10% reduction in population would necessarily be catastrophic. Four or five billion people can do a heck of a lot, particularly if their governments push engineering and science in schools. What it will mean is consolidation in the industries—fewer chip plants, slower development of new tech, etc. But for a real collapse you’d need a very large decrease in population, to the extent that it was no longer possible to retain technologically savvy communities, repair the basic infrastructure (telephones, telecom, electricity, water, sewage), etc.

I certainly agree that there is a threshold below which perturbations will not lead to collapse, and I won’t argue the point that a drop in population of 10% is above that threshold. The important point here is that technological progress is not elastic and cleanly reversible.

But let’s look more closely at the ability of the Roman Empire to harness modern technology. You mentioned the possibility of it getting steam engines and waterwheels working. Let’s take the easier case, waterwheels. Waterwheels were not invented in Mediterranean countries because they don’t have the climate for them—a fairly continuous supply of rainfall. Waterwheels are a useful technology only in sloping terrain fed by steady rainfall. Those conditions occur in some parts of Northern Europe. But there’s a catch: the kind of sloping terrain you need for waterfalls is the wrong kind of terrain for rain-fed agriculture. You need flat fields for crops. So now you have a third condition: flat fields not far from sloping terrain. We’re starting to narrow the applicability of the technology.

But there’s another problem: northern Europe was using slash-and-burn agriculture well into Roman times. The transition to the three-field rotation system had not yet begun. Which means that population densities were low. Which in turn means that the cost-effectiveness of a waterwheel is reduced because fewer people can bring their grain the long distances to the waterwheel.

Waterwheel technology is not particularly hard to figure out. People were using windmills in Mesopotamia long before Roman times, and Roman technology had plenty of big water projects and big wheel systems (there was even a technology using a huge wheel that slaves worked like gerbils in a toy wheel). I’m sure that the Romans figured out the concept of the waterwheel—they just never built it because it didn’t make economic sense for the low population densities available in the regions where it was possible.

The ancient Romans constructed numerous aqueducts (Latin aquaeductūs, sing. aquaeductus) to supply water to cities and industrial sites. These aqueducts were amongst the greatest engineering feats of the ancient world, and set a standard not equalled for over a thousand years after the fall of Rome. Many cities still maintain and use the ancient aqueducts even today, although open channels have usually been replaced by pipes.

The Romans typically built numerous aqueducts to serve any large city in their empire, as well as many small towns and industrial sites. The city of Rome itself, being the largest city, had the largest concentration of aqueducts, with water being supplied by eleven aqueducts constructed over a period of 500 years. Scholars can even predict the size of the city by its water supply. They served potable water and supplied the numerous baths and fountains in the city, as well as finally being emptied into the sewers, where they performed their last function in removing waste matter. The methods of construction are well described by Vitruvius in his work De Architectura written in the first century BC. His book would have been of great assistance to Frontinus, a general who was appointed in the late first century AD to administer the many aqueducts of Rome. He discovered a discrepancy between the intake and supply of water caused by illegal pipes inserted into the channels to divert the water, and reported on his efforts to improve and regulate the system to the emperor Nerva at the end of the first century AD. The report of his investigation is known as De aquaeductu.

In addition to masonry aqueducts, the Romans built many more leats; channels excavated in the ground, usually with a clay lining. They could serve industrial sites such as gold mines, lead and tin mines, forges, water-mills and baths or thermae. Leats were very much cheaper than the masonry design, but all aqueducts required good surveying to ensure a regular and smooth flow of water.

Maybe the aliens are so much more evolved and advanced compared to us that we cannot be aware of their existence. Just like a mushroom has no idea when you are standing two inches away from it. I sometimes wonder if being able to think and love is as good as it gets in this universe…

I think the argument that a major loss in population would result in a loss in technology is wrong. While a small population may not have the resources to invent or build technology, that’s wouldn’t be the case here. Let’s assume a catastrophe such as severe global warming, wholesale radiation from dirty nuclear devices, a worldwide plague, or even an astroid strike. Although the population would be decimated, a great deal of the technology would still be there. Some oil could still be pumped, a few power plants could still be operated. Machine shops would still function, some chemical laboratories and plants would still be there. While it would take a while to rebuild, enough of the artifacts of present civilization would still exist, that there would be a good base on which to rebuild.

The problem here, Occam, is that the inputs for every technological enterprise are themselves pretty specialized. For example, suppose you want to keep your hydroelectric dam functioning so that you have an electricity supply. That shouldn’t be too difficult, until you need to replace a worn-out part. Suppose that it’s a temperature-measuring instrument. To fabricate that instrument, you’ll need a plastics factory to make the housing, a wire-making facility for the wiring, copper mining and smelting to make the wire, more plastics to make the insulation, a printed circuit board facility to make the PCB for the instrument, chemical factories to manufacture the etching solution for the PCB creation, gold mining and smelting to make the gold contacts, lead and tin mining and processing for the solder, and of course all the equipment for all those mines and smelters, and lots of gasoline for the equipment, oil wells, pipelines, and refineries to provide that gasoline and the inputs for the chemical factories, a transportation system to move all those goods around between all those factories—do you see how the problem just explodes in your face? Where will get all the people necessary to operate all those facilities? And that’s just to replace a single temperature-measuring instrument. Now let’s talk about all the other equipment: transformers, bearing, generators, high-voltage insulators, high-current switches…